Safety and Risk Factors of Needle Thoracentesis Decompression in Tension Pneumothorax in Patients over 75 Years Old

Background There are very few professional recommendations or guidelines on the needle thoracentesis decompression (NTD) for the tension pneumothorax in the elderly. This study aimed to investigate the safety and risk factors of tension pneumothorax NTD in patients over 75 years old based on CT evaluation of the chest wall thickness (CWT). Methods The retrospective study was conducted among 136 in-patients over 75 years old. The CWT and closest depth to vital structure of the second intercostal space at the midclavicular line (second ICS-MCL) and the fifth intercostal space at the midaxillary line (fifth ICS-MAL) were compared as well as the expected failure rates and the incidence of severe complications of different needles. We also analyzed the influence of age, sex, presence or absence of chronic obstructive pulmonary disease (COPD), and body mass index (BMI) on CWT. Results The CWT of the second ICS-MCL was smaller than the fifth ICS-MAL both on the left and the right side (P < 0.05). The success rate associated with a 7 cm needle was significantly higher than a 5 cm needle (P < 0.05), and the incidence of severe complications with a 7 cm needle was significantly less than an 8 cm needle (P < 0.05). The CWT of the second ICS-MCL was significantly correlated with age, sex, presence or absence of COPD, and BMI (P < 0.05), whereas the CWT of the fifth ICS-MAL was significantly correlated with sex and BMI (P < 0.05). Conclusion The second ICS-MCL was recommended as the primary thoracentesis site and a 7 cm needle was advised as preferred needle length for the older patients. Factors such as age, sex, presence or absence of COPD, and BMI should be considered when choosing the appropriate needle length.


Introduction
Te elderly patient population is rapidly growing due to improvements in preventive health service and medical care, which leads to increasing populations of elderly trauma patient. According to 2016 National Trauma Databank (NTDB), 31% of trauma patients were at least 65 years old [1]. Elderly trauma patients have worse outcomes compared with younger patients with similar injuries [2][3][4][5]. Terefore, how to improve treatment of trauma in elderly patients is an important research topic.
Tension pneumothorax is a fatal disease causing acute and severe compromise of patients' ventilation and circulation, in which case immediate decompression is necessary for better prognosis [6]. A previous study has shown that the incidence of tension pneumothorax varies from 0.2% to 1.7% in patients with prehospital trauma [7]. Several trauma guidelines [8][9][10] recommend needle thoracostomy as a lifesaving intervention, with placement in the second intercostal space at the midclavicular line (second ICS-MCL), the fourth intercostal space at the anterior axillary line (fourth ICS-AAL), or the ffth intercostal space at the midaxillary line (ffth ICS-MAL) for tension pneumothorax in a prehospital environment. Although Te 5 cm thoracentesis needle was widely used in clinical practice [11], the failure rate of needle thoracostomy for tension pneumothorax is considerably high, ranging from 4% to 65% [12]. Inadequate needle length less than chest wall thickness (CWT) has been identifed as the main cause of failed decompression in many studies [13][14][15]. It has been controversial in recent years as to which position is most ideal for decompression in general and also in particular to age and ethnicities; some of the relevant studies and their fndings are showed in Table 1. In 2018, according to newly issued the Advanced Trauma Life Support (ATLS) guidelines, the ffth ICS-MAL was suggested as the preferred place, and an 8 cm needle rather than the common 5 cm needle was proved to increase success rate of adults' decompression [16]. Nevertheless, no specifc recommendations are made for older patients. Older patients are undergoing signifcant changes in their muscles, hearts, and lungs, thus the CWT may difer from ages. However, literature about the efect of age on the CWT in older patients is rare, and the appropriateness of an 8 cm needle lacks evidence.
Terefore, this study aims to compare two insertion points: the second ICS-MCL and the ffth ICS-MAL and to evaluate the ideal length of the thoracentesis needle based on the success rate and risk of severe complications. Besides, this study explored the infuence of age, sex, presence or absence of chronic obstructive pulmonary disease (COPD), and body mass index (BMI) on the CWT at diferent intercostal spaces to estimate the CWT and select the appropriate length of the thoracentesis needle.

Materials and Methods
Te study was authorized and approved by the Ethics Committee of Chinese PLA General Hospital (2022-041), and the requirement for consent was waived, as this was a retrospective study. Tis retrospective observational study included consecutive older patients in the Chinese PLA General Hospital, Beijing, from July 1 to 31, 2020. Patients aged ≥ 75 years and in-patients who underwent chest computed tomography (CT) were brought into the study. Patients with a history of chest surgery and patients whose arms were not raised above their heads in their chest CT images were excluded from the study. Clinical data, including patient age, sex, weight, height, and presence or absence of COPD, and imaging data were extracted from electronic medical document.

CWT Measurement.
CWT is the distance from the skin to the parietal pleura. Chest CT was performed on Optima CT660 (GE Medical Systems, Forchheim, Germany), which is a 128-detector scanner with tube voltage 120.0 kV and nominal single collimation width of 1.25 mm. First, a line was drawn along the clavicle on the coronal scout topogram, and the midpoint was marked. Ten, a vertical line bisecting the midpoint was dropped into the hemithorax to mimic the clinical determination and to estimate the midclavicular line. Te intersection point of the midclavicular line and the horizontal line crossing the inferior border of the second intercostal space (ICS) was considered as the insertion point at the second ICS-MCL (Figure 1(a)). Similarly, the midaxillary line was defned as the vertical line crossing the center of the armpit. Te intersection point of the midaxillary line and the horizontal line crossing the inferior border of the ffth ICS was considered as the insertion point at the ffth ICS-MAL (Figure 1(b)). Te cross-sectional slices obtained from CT were reconstructed into 5 mm-thick sagittal multiplanar reformatted images. Te corresponding insertion points at the second ICS-MCL and ffth ICS-MAL are shown in Figures 1(c) and 1(d). Considering that a longer needle will increase the incidence of severe complications, we assessed the safety of thoracentesis with the shortest depth to vital structure (DVSclose). Te DVSclose was the minimum distance from the skin to the vital intrapleural structures crossing the insertion point [11,17,18]; it is an index for measuring the safety of needle decompression. Tese vital structures included the pericardium, aorta, superior vena cava, inferior vena cava, large pulmonary vessels, and thymus gland [17].
Te radial depth, the shortest depth from the skin to the parietal pleura, was used as representative of the CWT in our study because the CWT varies when the insertion angle change. Measurements were made for each ICS: the radial depth and DVSclose of the second ICS-MCL and ffth ICS-MAL; the measurements were conducted on the left and right sides. Examples of these measurements are shown in Figures 2(a) and 2(b), respectively. In Figure 2, the segment AB denote the CWT and the segment AC denote the DVSclose of the insertion point.
Te thoracentesis was considered unsuccessful when the CWT exceeded the needle length. Te expected failure rate was calculated using the following equation: expected failure rate � (the number of measurements of CWT of the ICS that exceeded needle length/the number of overall measurements) × 100%. Severe complication should be considered when the DVSclose is less than the length of the needle. Te expected severe complication rate was calculated using the following equation: expected severe complication rate-� (the number of measurements of DVSclose of the ICS that was less than needle length/the number of overall measurements) × 100%.

Clinical Data Analysis. IBM SPSS Statistics for
Windows, version 22.0 (SPSS Inc., Chicago, IL, USA) was used for all statistical analyses. Te paired-sample t-test was used to compare the CWT and DVSclose between the second ICS-MCL and the ffth ICS-MAL in the same patient. Fisher's exact test was used to compare the expected failure rate and the incidence of severe complications. Ten,

Results
A total of 91 men and 45 women were fnally included in the study. Te average age of the patients was 84.9 ± 5.81 years, with a mean BMI of 23.22 ± 3.96 kg/m 2 . Te CWT, DVSclose, and diference of them between the second ICS-MCL and the ffth ICS-MAL are shown in Table 2. Te results of the pairedsample t-test showed that the CWT and DVSclose at the second ICS-MCL was both signifcantly less than that at the ffth ICS-MAL on both sides of the chest (P < 0.05). Tables 3 and 4, respectively, shows the diferences in the expected failure rate and the incidence of severe complications associated with 5 cm versus 7 cm needles and 7 cm versus 8 cm needles. Te results showed that success rate associated with using a 7 cm needle was signifcantly higher than that with using a 5 cm needle (P < 0.05), and the incidence of severe complications associated with using a 7 cm needle was signifcantly less than that with using an 8 cm needle (P < 0.05). However, the success rate of the 7 cm and 8 cm needles had no signifcant diference.
Multiple linear regression analysis showed that the CWT of the second ICS-MCL was signifcantly correlated with age, sex, presence or absence of COPD, and BMI (P < 0.05), whereas the CWT of the ffth ICS-MAL was signifcantly correlated with sex and BMI (P < 0.05). Coefcient of the multiple linear regression (β) of diferent independent variables for diferent insertion points are shown in Table 5.

Discussion
As there were few studies discussing the appropriate location and needle length of pneumothorax decompression in elder, it is important to evaluate the distribution of the CWT and DVSclose in older patients to improve the success rate of prehospital pneumothorax decompression and reduce insertion-related complications. Tis study compared the second ICS-MCL and the ffth ICS-MAL to determine a more appropriate insertion point and described the ideal thoracentesis needle length. In addition, the afecting factors of CWT were also analyzed.
Te choice of the insertion points and needle length was a widely studied question but remains controversial so far. In a study by Inaba et al. involving 20 cadavers [12], the success rate of using a 5 cm needle at the ffth ICS was 100%, whereas that at the second ICS was only 58%, indicating that the CWT at the second ICS was relatively thicker. A metaanalysis by Laan et al. indicated that the CWT at the fourth or ffth ICS-AAL was smaller than that at the second ICS-MCL in multiple populations [19]. Elhariri et al. pointed out that the CWT at the ffth ICS-MAL was signifcantly less than second ICS-MCL and an 8 cm length catheter had a better efcacy in comparison to 5 cm catheter [16]. Previous studies have mainly focused on adults, and there are only few studies on the CWT of the older population. Whether the recommendations for young adults are applicable to the older patients is debatable. Terefore, this study discussed the problem for the older patients and further explored the afecting factors of the CWT. Given tissue can be displaced by the pressure from the ultrasound probe, altering the CWT and leading to lower measurements than the actual values, CT was used as measurement method instead of ultrasound [20]. Serious complications, such as aortic injury, myocardial injury, and pericardial tamponade, were more likely to occur when using longer thoracentesis needles. Terefore, DVSclose was used as an indicator for the safety of thoracentesis needles in the study.
Te 2018 ATLS guidelines recommend the ffth ICS--MAL as the primary location for decompression of tension pneumothorax [16]. However, our research found that the CWT of the second ICS-MCL was signifcantly less than that of the ffth ICS-MAL both on the left and the right side. Consequently, the second ICS-MCL was associated with a higher success rate than the ffth ICS-MAL for older patients. In addition, according to the common sense, thoracentesis at the ffth ICS-MAL increase the difculty in transport of the patients and may increase the risk of catheter slippage. Te second ICS-MCL may be the better insertion point for older patients, with a thinner CWT and higher success rate.    Regarding needle length, several CT-based studies [20][21][22][23] have reported the inadequacy of a common used 5 cm thoracentesis needle for successful decompression. A meta-analysis by Clemency et al. showed that a 6.44 cm thoracentesis needle was needed for a 95% success rate and an 8 cm thoracentesis needle was needed for a 100% success rate at the second ICS-MCL [15]. Yamagiwa et al. pointed out that the CWT varies from nationalities or races [21]. Te average CWT at the second ICS-MCL in Japan is 3.06 cm, thus a 5 cm needle is appropriate for 94% of the patients. Tis study fnds that a lower expected failure rate of thoracentesis is associated with using a 7 cm needle compared with a 5 cm needle (P < 0.05). Meanwhile, a lower rate of severe complications is associated with a 7 cm needle than an 8 cm needle (P < 0.05). Te 5 cm thoracentesis needle can't achieve satisfactory goals of success depression but increased the risk of aerodermectasia, thus it was not recommended by the study. In addition, using the 7 cm thoracentesis needle reduced the probability of serious complications but did not signifcantly decrease the expected failure rate when compared with an 8 cm needle. Terefore, the 7 cm thoracentesis needle is recommended for prehospital decompression of tension pneumothorax for the older Chinese patients.
As for the afecting factors of CWT, many studies have shown that the chest wall of women is thicker than that of men at the second ICS-MCL and fourth or ffth ICS-MAL [13,21,22,24]. Inaba et al. [25] and Powers et al. [26] suggested that there is a relationship between the CWT of second ICS-MCL and BMI, but the relationship between BMI and the ffth ICS-MAL is unknown. Te present study showed that CWT of the second ICS-MCL was signifcantly correlated with age, sex, presence or absence of COPD, and BMI, whereas the CWT of the ffth ICS-MAL was signifcantly correlated with sex and BMI. It is obvious that patients with higher BMI or female patients, especially with rich subcutaneous tissue of the breasts, are inclined to have thicker CWT, while patients who have COPD tend to have the barrel chest [27], are inclined to have thinner CWT. Almost 20% of elderly can be diagnosed with sarcopenia, which would lead to skeletal muscle loss [28], suggesting that aging leads to a loss of chest wall muscle in older adults [29]. Due to the loss of muscles, older patients tend to have smaller CWT. It is noteworthy that the CWT of the ffth ICS-MAL was not signifcantly corrected with age and COPD. Te reason may be attributed to the less muscle in the ffth ICS-MAL, which may be not notably afected by age or COPD. Further researches should take more afecting factors into consideration and propose a predictive model of the CWT, so that accurate estimation can be achieved in the selection of thoracentesis needles.
Tis study had some limitations. First, this study only selected inpatients for data integrity; thus, the conclusions may have biased outcomes. Second, the measurement of the CWT relies on manual measurement by the imaging system, and the measurement error is difcult to control. Further research involving more population and using more precise measurement methods would be encouraging.

Conclusions
Tis study intended to recommend appropriate location and needle length and to explore the afecting factors of the CWT for older patients. Our study found out the CWT of the second ICS-MCL was signifcantly less in comparison to the ffth ICS-MAL both on the left and the right side. Terefore, we can induce that, diferent from the adults' primary thoracentesis site, the second ICS-AAL is the primary site for tension pneumothorax in Chinese patients over 75 years old. In addition, a 7 cm thoracentesis needle, with signifcant decrease in the incidence of severe complications, may be a better option than the 8 cm thoracentesis needle for Chinese patients over 75 years old. Doctors should mainly consider age, sex, presence or absence of COPD, and BMI when choosing the proper needle length.

Data Availability
Te datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Ethical Approval
Te authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Te study was authorized and approved by the Ethics Committee of Chinese PLA General Hospital (2022-041), and the requirement for consent was waived, as this was a retrospective study.

Disclosure
Ming Yin, Miao Lv, and Guogang Xu share senior authorship.

Conflicts of Interest
All authors have completed the ICMJE uniform disclosure form. All authors declare that there are no conficts of interest. All coauthors have agreed to publish the manuscript. Te manuscript has been read and approved by all the authors, the requirements for authorship have been met, and each author believes that the manuscript represents honest work.

Authors' Contributions
Yanhu Wang, Lei Wang, and Cheng Chen authors are contributed equally to this article and they share frst authorship. 6 Canadian Respiratory Journal